Barrel distortion is a lens defect that causes straight lines to bow out toward the edges of the image. Pincushion distortion is the opposite effect, where straight lines bend inward.

Examples of barrel distortion (left) and pincushion distortion (right)

Vignetting is a defect where the edges, especially the corners, of an image are darker than the center. Chromatic aberration appears as a color fringe along the edges of objects caused by the lens focusing on different colors of light in different planes.

Some lenses exhibit these defects depending on the focal length or the f‑stop used. You can set the Lens Correction filter to use settings based on the camera, lens, and focal length used to make the image.